Delay circuit for rectangular waves



Jan. 9, 1951 H. JOHNSON 2,537,589

DELAY CIRCUIT FOR RECTANGULAR WAVES Filed Dec. l5, 1945 /fw @MZM fwww/wu WAHI y H'g WAL/[Aro i lu l INVENToR. fif'zaz a/c cfodon I BY Patented Jan. 9, 1951 `'DELAY CIRCUIT FOR RECTANGULAR.WA VES I Harwick Johnson, Princeton, N. `Iil., "as'signorfto .Radio Corporation of America, vacorporation of .Delaware :Application December 15, 1945, Serial No. 635,376

2 Claims. 1

.My invention relates to wave shaping and time A`delay circuits and particularly'to apparatusfor obtaining the desired timing of rectangular waves.

An object of the invention is to provide an improved method of and means for obtaining a delayed rectangular wave.

Another object of the invention is to provide an improved method of and means for delaying a rectangular wave and adjusting its symmetry.

Another object of the invention is to provide a simplied circuit for delaying and shaping a rectangular wave.

Still another object of the invention is to provide an improved differentiating circuit.

In practicing one embodiment of the invention the rectangular wave is passed through a difierentiating circuit that is designed to produce positive and negative pulses that preferably are separately adjustable in width or shape. The resulting differentiated wave is reversed in polarity and combined with the rectangular wave. The combined wave is then clipped to obtain the desired rectangular wave having delayed front and back edges.

The invention will be better understood from the following description taken in connection with the accompanying drawing in which Figure 1 is a block diagram of one embodiment of the invention,

Figure 2 is a group of graphs that are referred to in explaining the invention,

Figure 3 is a block diagram of another embodiment of the invention, and

Figures 4 and 5 are circuit diagrams of differentiating circuits designated in accordance with one feature of the present invention.

In the several figures, similar parts are indicated by similar reference characters.

Referring to Fig. 1, a square wave or rectangular wave generator IEB supplies a wave II to a differentiating circuit I2 whereby a differentiated wave I3 is produced. The wave I3 is reversed in polarity by a polarity reversing circuit ill to produce the wave I6 which is supplied to an adding circuit I l.

The rectangular wave il is also supplied over a conductor I8 to the adding circuit il so that a wave of the shape shown at lil is obtained which is the sum of waves II and i6. The wave I9 is then passed through a clipper or limiter circuit 2| to obtain a rectangular wave 22 having delayed front and leading edges.

The time relation of the various wave forms is apparent from an inspection of Fig. 2 although .the graphs vof `Fig. f2 are "for an embodimen wherein lthepositiveand negative differentiated pulses are of different durations. Such pulses of different durations may be obtained by employing a differentiating circuit such as shown in Fig. 4 or Fig. 5. The graphs shown in Fig. 1 are for the case where the positive and negative pulses of wave I3 are of equal duration, in which case the differentiating circuit may be conventional.

Referring to Fig. 4, the differentiating circuit comprises a pair of diodes 26 and 21 connected to pass current in opposite directions, and each connected in series with an inductance coil 28. Variable resistors 29 and 3| are connected in series with the diodes 26 and 21, respectively.

The positive half cycle of the applied rectangular wave is passed by the diode 21 and the duration and shape of the resulting positive pulse appearing across the coil 28 may be changed by adjusting the value of the resistor 3|. Similarly, the duration and shape of the negative pulse may be changed by adjusting the Value of the resistor 29. The graphs in Fig. 2 show how both the timing and the symmetry of a rectangular wave may be adjusted by employing -the differentiating network of Fig. 4 in the circuit shown in Fig. 1, the circuit of Fig. 4 being represented in this case by the block I2.

Fig. 5 shows another differentiating circuit that may be employed the same as that of Fig. 4. A small capacitor `32 is connected in series with the diodes 26 and 21, and the positive and negative differentiated pulses are adjusted by resistors 33 and 34, respectively.

Fig. 3 shows an embodiment of the invention wherein the differentiated wave I3 is reversed in polarity and clipped by a polarity reverser and clipper circuit 36 to produce the positive and negative pulses of wave 31.

The wave 31 and the wave l I are added in the circuit I1 to produce the substantially rectangular Wave 38 which is squaredup by the limiter 2l to obtain a good rectangular wave 39 which does nothave rounded corners.

The timing of the front and back edges of the rectangular wave 39 is determined by the widths of the negative and positive pulses, respectively, of the wave 3l. The widths of these pulses are determined by the differentiating circuit adjustment and by the clipping levels in the limiter 36. The differentiating circuit I2 may be one of the circuits shown in Figs. 4 and 5 where it is desired to make the widths of the positive and negative pulses of the wave 31 independently adjustable.

I claim as my invention:

1. A circuit for delaying both the front and back edges of a substantially rectangular wave, said circuit comprising differentiating means arranged to provide a differentiated wave consisting of positive and negative pulses each of which has a trailing edge and each of which is adjustable in Width with respect to the other, means for adding said differentiated wave and said rectangular wave in polarity opposition to obtain a combined wave which has the wave shape of a rectangular Wave with sloping front and back edges, and means for clipping said combined Wave at two different voltage levels to obtain a rectangular wave having delayed leading and trailing edges.

2. The invention according to claim 1 wherein said differentiating means comprises a pair of rectiers connected in shunt and also connected in opposite current-conducting directions with respect to the applied signal, a pair of variable HARWICK JOHNSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Nuttall May 7, 1940 Beale et al. Aug. 12, 1941 Och et al Dec. 10, 1946 Greig Apr. 29, 1947 Wheeler May 27, 1947 Number 

